40 HORTICULTURAL SOCIETY OF NEW YORK. 



Colorado has a half-dozen or more distinct climates, while 

 Nebraska, though more uniform, shows markedly different cli- 

 mates in prairie, sandhill and foothill region. 



The use of instruments for measuring all the physical 

 factors of the plant's environment is imperative if we are to 

 know exactly what conditions the plant has to meet, and how it 

 meets them. Furthermore, it is only in this way that we can 

 discover real differences between habitats, or climates, determine 

 the best source for promising forms, decide upon the most prac- 

 ticable method of treatment, and forecast the probable outcome. 

 The exact measurement of the water of the soil, and the humidity 

 of the air, of light, temperature, evaporation, win,d, soil salts, 

 exposure, slope, etc., will work a revolution in the methods and 

 results of plant introduction and plant evolution. It will force 

 attention to the fact that regions and areas which possess es- 

 sentially the same climate, or weather, really show physical dif- 

 ferences of the greatest importance to the experimenter. Finally, 

 it seems probable that exact ecological methods of this kind 

 will demonstrate that all variation is first or last only a question 

 of environment; that the minute variations of plants, as Dar- 

 win understood them, can be traced to minute physical differ- 

 ences of the habitat, and that, as the final crown of the work, 

 measured sets of physical factors and measured habitats can be 

 made to produce definite desired adaptations in both cultivated 

 and native plants. 



The President Cannot you supplement it with remarks, Dr. Mac- 

 Dougal ? 



Dr. MacDougal I find much in this paper which is in accord with 

 my own views. I rather object to anyone picking out any one physical 

 factor and saying it is the keynote of the business, because it is not. He 

 might as well say the left hind wheel of a wagon is most important, but 

 it is not ; on the other hand, the four wheels are equally important, and 

 they get out of line unless all four are together. When Professor Clements 

 says the soil moisture is the most important factor in a given situation, he 

 is considering something to be a fact which is not a fact. In the main, 

 however, I think I can say that I agree with him in the principal things. 



Mr. H. A. Siebrecht There is one thing I notice in this connection, 

 and that is that the plant or tree suffers more from dryness or drought 

 in cold weather. That I have experimented with myself, I find it is a fact, 

 and I have often spoken of it in this way, to use a common every-day 



